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On my last build, I had a gap between the fingerboard and the body because of the 25' radius. How do I eliminate that gap? I thought if I angle the neck just right it will close that gap, but then the problem is the bridge and the saddle needs to be very large in order to have a high enough action for playing.

Is 25' too much for a top? What if I go with a shallower radius like 40' or even 60'?

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

For me, the top if flat upside the soundhole.

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Francis Richer, Montréal
Les Guitares F&M Guitars

I sand the top so its flat where the fingerboard goes over the body...but im not quite sure where you mean the gap is.

Your two choices are to shim the fingerboard tongue, or plane/sand some off the very end of the fingerboard.
I use a 60 foot radius on the #1 cross brace in the upper bout. That tends to produce a straight fingerboard with a reasonable neck angle.
The way I look at it, there is no good reason to build a top with a constant radius. My X-braces have a 25 foot radius above the bridge, but are flat below. The tone bars and finger braces are also flat. The idea: that shape is better for resisting the torque on the top at the bridge, and it works very well. When compared to the plane of the edges of the top (I glue the top to a flat rim), the bridge is slightly tilted back before the strings are tightened. With full tension, the bridge is parallel with the edge of the body.

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John

John has offered two workable solutions (the second requiring that you set the neck a little deeper in its mortise). You could also sand a flat as wide as the fingerboard, running from the sound hole to the neck end, then gradually lower your neck tenon into the mortise until the bottom of the fingerboard is flush with the flat.

I was just thinking, what about 25' for the rest of the top (X-brace, tone bars, etc) and flat but thicker UTB? The only issue I see here is how would I glue up the bracing with different radius?

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Should I sand the top rim with the dish, or is it better if I simply sanded it flat?

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com